I. Technical Field
The present invention relates to a cooling storage cabinet having an inverter compressor and an operating method thereof.
II. Description of the Related Art
In recent years, refrigerators, such as for commercial use, and having inverter compressors, have become widely used. The inverter compressor can perform speed control. By using the inverter compressor, there are many advantages, one of which is higher efficiency in performing control cooling. That is, in a case of performing control cooling to maintain an inside of the refrigerator around a set temperature, rotational speed (revolution number per unit time) of the inverter compressor is controlled to be reduced stage by stage in the vicinity of the set temperature. By adopting this control method, a continuous ON time of the compressor becomes much longer; in other words, the number of switching between ON and OFF is considerably reduced. Furthermore, the compressor is driven at a lower rotation. Therefore, higher efficiency and energy conservation can be attempted.
Specifically, the applicant of the present application proposed an operating method as disclosed in Japanese Unexamined Patent Application Publication No. 2005-121341. This method is as follows. The rotational speed of the inverter compressor can be changed to a plurality of stages. A cooling characteristic that shows a target time-varying change mode of internal temperature drop is prestored as data in a storage means or device. At every predetermined sampling time, a target internal temperature drop rate based on the cooling characteristic is compared with an actual internal temperature drop rate calculated based on a value detected by an internal temperature sensor. In a case where the actual temperature drop rate is lower than the target temperature drop rate, the rotational speed of the inverter compressor is increased by one stage. In a case where the actual temperature drop rate is higher than the target temperature drop rate, the rotational speed of the inverter compressor is decreased by one stage. Thus, the internal temperature is controlled to be dropped in accordance with the prestored cooling characteristic.